Department of Radiation Oncology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands; Cancer Center Amsterdam, Amsterdam, The Netherlands.
Department of Radiation Oncology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2024 Feb 1;118(2):543-553. doi: 10.1016/j.ijrobp.2023.08.049. Epub 2023 Aug 25.
Selection and development of image guided strategies for preoperative gastric radiation therapy requires quantitative knowledge of the various sources of anatomic changes of the stomach. This study aims to investigate the magnitude of interfractional and intrafractional stomach motion and deformation using fiducial markers and 4-dimensional (4D) imaging.
Fourteen patients who underwent preoperative gastric cancer radiation therapy received 2 to 6 fiducial markers distributed throughout the stomach (total of 54 markers) and additional imaging (ie, 1 planning 4D computed tomography [pCT], 20-25 pretreatment 4D cone beam [CB] CTs, 4-5 posttreatment 4D CBCTs). Marker coordinates on all end-exhale (EE) and end-inhale (EI) scans were obtained after a bony anatomy match. Interfractional marker displacements (ie, between EE pCT and all EE CBCTs) were evaluated for 5 anatomic regions (ie, cardia, small curvature, proximal and distal large curvature, and pylorus). Motion was defined as displacement of the center-of-mass of available markers (COM), deformation as the average difference in marker-pair distances. Interfractional (ie, between EE pCT and all EE CBCTs), respiratory (between EE and EI pCT and CBCTs), and pre-post (pre- and posttreatment EE CBCTs) motion and deformation were quantified.
The interfractional marker displacement varied per anatomic region and direction, with systematic and random errors ranging from 1.6-8.8 mm and 2.2-8.2 mm, respectively. Respiratory motion varied per patient (median, 3-dimensional [3D] amplitude 5.2-20.0 mm) and day (interquartile range, 0.8-4.2 mm). Regarding COM motion, respiratory motion was larger than interfractional motion (median, 10.9 vs 8.9 mm; P < .0001; Wilcoxon rank-sum), which was larger than pre-post motion (3.6 mm; P < .0001). Interfractional deformations (median, 5.8 mm) were significantly larger than pre-post deformations (2.6 mm; P < .0001), which were larger than respiratory deformation (1.8 mm; P < .0001).
The demonstrated sizable stomach motions and deformations during radiation therapy stress the need for generous nonuniform planning target volume margins for preoperative gastric cancer radiation therapy. These margins can be decreased by daily image guidance and adaptive radiation therapy.
术前胃放射治疗的图像引导策略的选择和发展需要定量了解胃的各种解剖变化来源。本研究旨在使用基准标记和 4 维（4D）成像来研究胃的分次间和分次内运动和变形的幅度。
14 例接受术前胃癌放射治疗的患者在胃内分布 2 至 6 个基准标记（共 54 个标记）和其他影像学检查（即，1 个计划 4D 计算机断层扫描[pCT]，20-25 个治疗前 4D 锥形束[CB]CT，4-5 个治疗后 4D CBCT）。在进行骨性解剖匹配后，在所有呼气末（EE）和吸气末（EI）扫描中获得标记的坐标。评估了 5 个解剖区域（即贲门、小曲率、近端和远端大曲率、幽门）的分次间标记位移（即，在 EE pCT 和所有 EE CBCT 之间）。运动定义为可用标记的质心（COM）的位移，变形为标记对距离的平均差异。量化了分次间（即，在 EE pCT 和所有 EE CBCT 之间）、呼吸（在 EE 和 EI pCT 和 CBCT 之间）和预-后（治疗前和治疗后 EE CBCT）的运动和变形。
分次间标记位移因解剖区域和方向而异，系统和随机误差分别为 1.6-8.8 毫米和 2.2-8.2 毫米。呼吸运动因患者而异（中位数，3 维[3D]幅度 5.2-20.0 毫米）和日（四分位距，0.8-4.2 毫米）。关于 COM 运动，呼吸运动大于分次间运动（中位数，10.9 比 8.9 毫米；P<0.0001；Wilcoxon 秩和检验），而分次间运动大于预-后运动（3.6 毫米；P<0.0001）。分次间变形（中位数，5.8 毫米）明显大于预-后变形（中位数，2.6 毫米；P<0.0001），而预-后变形大于呼吸变形（中位数，1.8 毫米；P<0.0001）。
在放射治疗期间观察到的胃运动和变形幅度较大，这强调了术前胃癌放射治疗需要为非均匀计划靶区提供充足的边界。通过每日图像引导和自适应放射治疗，可以减少这些边界。
